Telecommunication networks are evolving due to the ever increasing variety of types of traffic that must be carried, such as broadcast and multicast services (e.g. Internet Protocol Television (IPTV), pay-per-view services, video on demand, gaming, high-definition personal video conferencing) as well as more conventional traffic types. The need to deliver such services requires a transport architecture based on a single network infrastructure, since the cost of operating and maintaining multiple service-specific networks is untenable.
In metro networks, there is a gradual migration from legacy Synchronous Digital Hierarchy (SDH)/Asynchronous Transfer Mode (ATM) technology towards solutions based on a combination of emerging Carrier Ethernet technologies such as Provider Backbone Bridge Traffic Engineering (PBB-TE, IEEE 802.1Qay) and Multi-Protocol Label Switching Transport Profile (MPLS-TP), with an intelligent optical transport layer, based on the Optical Transport Network (OTN) G.709 standard, supporting wavelength and sub-wavelength switching. While this approach allows a range of different traffic types to all be carried in a similar manner, within Ethernet frames, a significant amount of processing is required at each packet-forwarding node. Each node maintains a forwarding information base (FIB) which instructs the node where to forward each received packet. Every time a packet is received at the node, a header of the received packet is inspected and a look-up operation is performed in the forwarding information base. The forwarding should be performed as quickly as possible to minimise forwarding delay. It can require significant processing resources at a node to provide a suitable forwarding performance. Another disadvantage of this architecture is that it requires the complex OTN multiplexing hierarchy and a multi-layer switching structure, which results in an expensive network solution with limited scalability and flexibility.